Suppose for a moment that God is not the only self-existent one in the universe. Suppose for a moment that there is a part of man known as his intelligence that has always existed and is coeternal with God. Now suppose that those self-existing intelligences are not perfect like God but are subject to progression. If this were the case, then God could not create something that is itself self-existing. A self-existing intelligence would have its own free will. In order to help these self-existing intelligences progress, God could give them a spirit body from the elements that are eternal. In this way they become the spirit children of God. God could then want his spirit children to have a knowledge of good and evil and send his spirit children to a fallen mortal world and endow them with physical bodies made from elements that are eternal. In this way the intelligences progress by gaining spirit bodies and then physical bodies to become like God but go through a mortal world to learn that there is opposition in all things and when you have good you also have evil and that it is best to choose the good. After experiencing this mortal world, these mortal bodies experience death but are later resurrected to enjoy an immortal body of flesh and bones for all eternity.
Since God could not create our intelligences, and since our intelligences are imperfect, having his children experience good and EVIL allows them to progress. One must keep in mind that man's intelligence is eternal and after receiving a spirit body his spirit becomes immortal and finally after experiencing this mortal life and learning good and evil his mortal body is resurrected to become immortal and eternal to exist for ever and ever. In this way God brings about the progression of mankind's eternal intelligence. God allows evil because it is an eternal principal that there is opposition in all things. If God creates good, its opposite automatically exists. For mankind to become good beings, they must, with their free agency, learn to choose good over evil. God has placed mankind into a temporary world of good and evil so that man can experience good from evil and learn to choose good over evil of his own free will and choice. Only in this way can a self-existing intelligence progress toward becoming more like God.
Some may suppose that God is all powerful and can do absolutely anything imaginable. But that is not the case. God is only all powerful in that he can do all that is possible. There are eternal impossibilities that not even God himself can do. Some examples are that God cannot be an all good being and an all evil being simultaneously. God also cannot cease to exist. That which has a self-existent nature cannot cease to exist. Mankind's intelligence, also being self-existent, cannot cease to exist. Another eternal impossibility is that God cannot create things from nothing. Worlds were created out of self-existing matter and mankind and animals were created out of self-existing intelligence and matter. To create does not imply creation out of nothing. God is the great organizer of the universe. He creates things from self-existing intelligence and matter.
John 17:3
3 And this is life eternal, that they might know thee the only true God, and Jesus Christ, whom thou hast sent.